Picked up one of these the other day for my Gridseeds:
http://www.frys.com/product/5665801?site=sr:SEARCH:MAIN_RSLT_PGIt was ~$20 in-store at the time. Amazon didn't have them...don't know where else you might find them that might be cheaper. In any case, it's a 7-port hub with a 3.6A power supply bundled with it. Instead of the dinky 1.35mm (?) power connector you see on most hubs, it has the same 2.1mm connector that the Gridseed miners use, so you could pull an unused 5V output from your power supply and run the hub with that. I expanded from 6 to 8 miners today, so all seven ports are in use (plus a port on another hub). So far, all's well and it's cranking about 2.75 MH/s.